Dynamoelectric machine insulators

ABSTRACT

Electrical insulators are formed from insulative strip material by providing a substantially continuous ultrasonically welded seam. In one embodiment a tubular insulator for covering stator winding connections is formed by continuously moving the strip and a strip of dissimilar material about a cylindrical former having its axix in generally the same direction as the direction of elongation and motion of the strips to thereby form a multiple layer sleeve with a seam being ultrasonically formed to include the two edges of the strip of polyester material. In a second embodiment two or more parallel elongated narrow flat strips are moved in their direction of elongation with a plurality of flat sheets of polyester material being ultrasonically bonded thereto along a substantially continuous seam on the individual sheets with the individual sheets occurring at uniform intervals along the strips to thereby form a ladder-like strip of insulators. In both embodiments the strip is periodically severed after bonding to form individual insulators. In the case of the second embodiment this severing occurs along a line substantially perpendicular to the direction of elongation of the strips, and in a manner to separate the flat sheets into two approximately equal pieces to thereby form phase insulators for stator windings. Substantially continuous ultrasonically formed seams are achieved with surprisingly little tool wear. Tools are case hardened at least along the surface engaging portions or welding tips thereof. Relatively continuous welded seams are achieved by providing ultrasonic vibrations to the tool tip.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of my copending application Ser. No.536,946 filed Dec. 23, 1974, now U.S. Pat. No. 4,100,005, which is acontinuation-in-part of my then copending application Ser. No. 333,786filed Feb. 20, 1973, which subsequently issued as U.S. Pat. No.3,880,194 on Apr. 29, 1975, and the entire disclosures of both of saidapplications are hereby incorporated herein by reference.

U.S. Pat. No. 3,748,510, which issued July 24, 1973 from my applicationfiled Oct. 26, 1971, assigned to the assignee of this application is arelated patent, and the entire disclosure of said patent is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to new and improved insulators for use indynamoelectric machine stator assemblies including insulators formed byjoining together different pieces of materials along a continuousultrasonically welded seam.

The manufacture of dynamoelectric machines has developed into a highlysophisticated industry. In the manufacture of wound stators for suchmachines, coils may be wound on a coil form and then inserted into thestator; or the wire for forming such coils may be directly dispensedinto the stator slots in a so-called "in-slot" winding process. Ineither approach, various insulators are employed in addition to thetypical ground insulation that is immediately adjacent to coilaccommodating surfaces of the core. For example, an exemplary statorslot may have a cuffed stator slot wedge or slot liner, such asillustrated in U.S. Pat. No. 2,935,859, inserted therein before any wireis deposited in that slot, although slot insulation may also take theform of an epoxy or other resinous coating. With the slot liner inplace, a first phase winding may then be inserted in the slot to befollowed by a phase insulating wedge or separator. Next, a secondwinding is inserted in this slot and, lastly, an insulating wedge isinserted in the slot. In this example, where two different phasewindings occupy the same slot, it is also desirable to provideadditional insulation between the end turns of the two different phases.This additional end turn insulation is sometimes called "window"insulation in the art, and an example of such an approach is shown inU.S. Pat. No. 2,701,317, which was assigned to the assignee of thisapplication. There may also occur connections between different polewindings of the stator and connections from such windings to the statorleads. To insulate such connections, there may be provided additionalinsulators often in the form of insulators or sleeves such as thosedisclosed in U.S. Pat. No. 3,219,857 (which is assigned to the assigneeof this application), which fit over the interconnected wires and toeither side of a particular point of connection. Since these interpoleor external lead connections are often soldered, sharp protrusions maybe present, and the tubular insulators should be particularly rugged.Stator insulators have at one time or another been manufactured of paperand also of polyester materials, such as polyethylene terephthalatewhich may be purchased under the trademark "Mylar" polyester. Thepolyester materials have proven to be particularly desirable materialsbecause of their strength, good electrical insulating properties, andcompatibility with lubricants and refrigerants normally encountered inhermetically sealed refrigeration compressor motor parts.

In a hermetically sealed compressor environment, quality of insulationis particularly important since such insulation comes in contact withrefrigerant and lubricants employed in the refrigeration system and anyinsulation failure may result in loss of not only the motor but anentire compressor unit. Any moisture which might be present in theinsulators at the time of assembly could of course lead to system damageif that moisture were to subsequently freeze and block the refrigerantcirculation path. Because of these considerations such insulators arenow almost universally fabricated from synthetic materials, of whichpolyethylene terephthalate or Mylar polyester will be taken as exemplarythroughout the present specification.

While polyethylene terephthalate is particularly suited to the hermeticmotor environment, it can be a difficult material to work with and israther costly. Heating this material in an attempt to bind two pieces ofpolyester sheet material together results in a thermal degradation ofthe material which not only weakens the material but also changes itschemical properties somewhat so that the material may be more prone toabsorb moisture. Also, if it is overly heated, refrigerants such asFreon may later cause a molecular particle to leave the insulator andcontaminate the Freon base refrigerant. Attempts have been made to bondtwo sheets of polyethylene terephthalate together by ultrasonic spotwelding techniques. However, such welds are not characterized by greatstrength, and I have found that ultrasonic welding of such material isso detrimental to the ultrasonic welding tips that such tips wouldrapidly wear away and require replacement. Adhesive or solvent bondingof polyester to polyester is expensive, does not result in particularlystrong bonds, and introduces undesirable materials which again may bedetrimental in a refrigerant compressor environment.

Present production techniques of, for example, phase insulators is tocut the insulator from a flat sheet of material and discard almost asmuch material as is retained for the end turn or phase insulator. Thecost of discarding such a substantial quantity of insulating material isof course substantial.

It is accordingly a general object of the present invention to overcomeone or more of the foregoing problems.

It is another object of the present invention to provide new andimproved electrical insulators from strip insulating material.

A further object of the present invention is to provide new and improvedand economical phase insulators for dynamoelectric machine statorwindings.

A still further object of the present invention is to provide new andimproved insulators including polyester materials joined togetherwithout degrading the materials.

A yet further object of the present invention is to provide new andimproved insulators having a substantially continuous polyester materialto polyester material ultrasonically welded seam.

It has been recognized in the art that ultrasonic welder tip wear is asubstantial problem, and particularly so in connection with weldingpolyester materials such as polyethylene terephthalate. In fact, theindustry makes use of exotic welder tip materials such as titaniumalloys, in an effort to reduce welder tip wear. Attempts to harden thetip or portion of the machinery which transmits the ultrasonicvibrations to the material being processed have not been successful,since hardening the vibration transmitting material would substantiallydiminish its vibration transmitting capabilities. In addition, hard orbrittle materials would rupture, crack or break when driven withsufficient energy to ultrasonically weld a work piece.

It is accordingly another object of the present invention to provide newand improved insulators while overcoming the problems associated withwear of an ultrasonic welding tip.

SUMMARY OF THE INVENTION

In carrying out the above and other objects in preferred embodiments, Iprovide a system for the production of polyester insulators that may beused in motor parts for hermetically sealed compressor applications. Oneform of insulator is used to separate end turns of different windingphases; and another form is used to cover winding connections. In theanother form, the insulators comprise generally tubular laminatedelectrical insulating sleeves having two wall areas which are, forexample, three layers thick. The insulator includes a section alongwhich a continuous weld seam is formed. In one three layer area, amaterial such as DuPont's Nomex polyamide insulating material issandwiched between two sheets or layers of a polyester material such asDuPont's Mylar polyester material. An exemplary three layered insulatormay comprise one sheet of Mylar material and one sheet of Nomexmaterial, but formed about a cylindrical rod so that the Mylar sheet iswrapped upon itself and overlapped so that a polyester to polyester topolyester ultrasonic bond may be established and thus also form a threelayer area.

In the above mentioned one form, the insulators may be used for "phase"or end turn insulation; and comprise at least one strip of relativelyflat insulation having at least one elongate narrow strip of polyestermaterial ultrasonically welded thereto. Preferably, two insulatingstrips are held together with two elongate narrow strips by continuouslywelded seams running generally in the direction of the elongate strips.Each flat sheet may be cut in a direction substantially perpendicular tothe longitudinal direction of the elongate strips so as to form two endturn insulating portions from each flat sheet. The substantiallycontinuous ultrasonically welded seam or polyester to polyester bond isachieved with an ultrasonic welding tip made of conventional cold rolledsteel but having the surface thereof hardened. Surprisingly, thisprovides a work piece engaging surface which is not plagued by problemsof wear and yet provides an ultrasonic welding tip having good vibrationtransmitting characteristics.

In preferred forms of the invention, the substantially continuousultrasonical welding is accomplished so that no unattached extremitiesof the elongate narrow strip exist.

BRIEF DESCRIPTION OF THE DRAWING

The aforementioned and other objects, features, and advantages of thepresent invention will become more apparent from the following detaileddescription thereof when considered in conjunction with the drawings.However the exemplifications set out herein illustrate the preferredembodiments of the invention in one form thereof, and suchexemplifications are not to be construed as limiting in any manner.

FIG. 1 is a side view of a winding connection insulator embodying thepresent invention in one form;

FIG. 2 is an end view of the insulator of FIG. 1 after forming and priorto ultrasonic welding;

FIG. 3 illustrates the ultrasonic welding or bonding of a continuousseam on the insulator of FIG. 1;

FIG. 4 is an end view like FIG. 2 but after the welding process has beenperformed;

FIG. 5 illustrates an overall method of forming the insulator of FIG. 1;

FIG. 6 is a perspective view of a fabricated phase insulator embodyingthe invention in another form;

FIG. 7 is a sectional view along the line 7--7 of the insulator of FIG.6 illustrating the fused bond thereof;

FIG. 8 illustrates a method of fabricating the insulator of FIG. 6;

FIG. 9 illustrates the continuous ultrasonic welding step of FIG. 8;

FIG. 10 is an end view of the ultrasonic welding tip shown in FIG. 9;

FIG. 11 is a view, with parts removed and parts broken away, thatillustrates the interrelationships of a phase insulator and a connectioninsulator of my U.S. Pat. No. 3,748,510; and

FIG. 12 is a view in perspective, partially broken away to show detail,of a portion of a stator assembly after it has been fabricated, with theconnection insulator from my U.S. Pat. No. 3,748,510 installed andwinding end turns compacted and tied and with phase insulatorstherebetween.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The structure of the insulator 11 of FIGS. 1 through 5 is most easilyunderstood beginning with FIG. 2 which shows an end view of thatinsulator 11 after it is formed but before being ultrasonically welded.The insulator comprises a strip 13 of polyester material (e.g., Mylar)which is wrapped about itself into a cylindrical form and of a diameterso as to complete slightly more than two complete revolutions. Thisallows the two edges of the strip 13 to overlap for subsequent welding.Before forming the strip in this manner a second strip 15 of adissimilar material such as the Nomex material is superimposed on thestrip 13 so that in the forming process the Mylar makes at least onecomplete revolution about a former so as to prevent the strip 15 fromcoming into contact with the former. The Mylar and Nomex (both of whichnames are registered trademarks of E. I. du Pont de Nemours and Company)strips are continuously fed to a former so as to continuously create atubular structure having a cross section like that illustrated in FIG.2. As is well known to persons of ordinary skill in the art, Nomex strip(or sheet) material is a high temperature-resistant nylon paper that isa polyamide material.

The former itself may comprise a cylindrical rod 17 as shown partiallyin cross section in FIG. 3. The width of the strip 13 is somewhatgreater than twice the girth of the cylindrical rod 17 so that the strip13 will wrap about the rod 17 somewhat more than twice, and the width ofthe strip 15 is somewhat less than the girth (or circumference) of rod17. The strip 15 is asymmetrically placed on the polyester strip 13 sothat material 13 is exposed along one side thereof, and such exposedside is started about the rod 17 so that the configuration of FIG. 2will result. The process of forming the continuously fed superimposedstrips 13 and 15 into the configuration illustrated in FIG. 2 isaccomplished by the former 19 of FIG. 5, and is not set out in furtherdetail here, since it is not necessary to an understanding of thepresent invention. Once the material is formed into the configurationshown in FIG. 2, that portion of its periphery having three adjacentlayers of strip 13 is passed under the welding head 21 of FIG. 5. As thelaminated tube 11 passes under welding head 21, it is still wrappedabout the cylindrical rod 17 which functions to support the materialunder the welding head 21. The rod 17 may be supported within the former19 in cantilever fashion and may be counterbalanced, for example, so toforce the polyester material upwardly toward the welding head 21.Alternatively, the rod 17 may be fixed in cantilever fashion and thewelding head 21 biased toward rod 17 so as to exert pressure on thethree layers of strip 13 between the welding tip and rod 17. The weldinghead itself is seen in greater detail in FIG. 3 and may comprise avibration transmitting portion or shank 23; and a tip 25. These twoportions are rigidly connected, in a mechanical sense, and may be formedas integral members or the tip 25 may be formed as a separatereplaceable portion. The tip 25 is caused to vibrate at an ultrasonicrate by standard ultrasonic welding techniques.

For example, the welding device may have a power supply for providingelectrical energy, means for converting the electrical energy intomechanical energy, and means for transferring the mechanical energy byway of the vibration transmitting portion 23 to the tip 25. The tip 25is continuously ultrasonically energized and the sheets 13 and 15 arecontinuously moved past the tip 25 so as to provide a continuous seam orbond between the three layers of polyester material 13. The ultrasonicvibrations cause motion between the polyester layers, thus inducingfrictional heat along their surfaces sufficient to fuse the materialstogether in the area of the weld or weld means without, however, heatingthe material 13 to a point where thermal degradation takes place.

As noted earlier, the welding tips used in the ultrasonic welding ofpolyester materials experience excessive wear. I can now overcome thatproblem by making the tip 25 of cold rolled or cold drawn steel and thencase hardening at least the work engaging portion thereof. This casehardening (or other suitable surface hardening) of the welding tip doesnot substantially diminish its vibration transmitting characteristics,but does provide an extremely hard surface that is not readily worn awayas strip 13 is moved therepast.

As the material of tube 11 passes beyond the welding head 21 of FIG. 5,it has the configuration illustrated in FIG. 4, where dotted linesillustrate the weld regions between the three layers of material 13. Asseen in FIG. 4 the tube 11 is formed as a generally tubular, laminated,electrical insulating sleeve having two wall areas which are threelayers thick. However, it should be clear that the process of formingthese materials about the cylindrical rod 17 could, for example, includeseveral more revolutions of the polyester material about the rod andcould include additional Nomex layers as well.

With reference again to FIG. 5, after welding, the tube continues to astation indicated generally as 27 where it is periodically severed so asto form the individual insulators 11. In one preferred embodiment,interpole and winding lead connection insulators for hermetically sealedrefrigeration units were manufactured in accordance with the presentinvention employing a cylindrical rod 17 having a one quarter inchdiameter. The Mylar-Nomex-Mylar insulating sleeves produced were about9/32 of an inch in diameter. The Mylar was about 0.003 to 0.005 inchthick and 1 7/8 inches wide; while the Nomex was 0.003 inch thick and3/4 of an inch wide. Both materials were fed to station 19 from reels ofstrip material. The severing device 27 was actuated at a rate such as toproduce insulators 11 having an axial length of slightly over 2 inches.

Ladder-like insulators of the same general configuration as thatillustrated in perspective in FIG. 6 are employed in dynamoelectricmachine stators where the end portions 29 and 31 function to separatethe end turns of different winding phases. The connecting portions orsegments 33 and 35 pass along a pair of stator slots between the endfaces of the stator core. The width of the connecting portions 33 and 35must be such that they will fit within stator slots and the distancebetween the two end portions 29 and 31 should be slightly greater thanthe axial length of the stator in which the insulator of FIG. 6 is to beused. The distance between the end portions 29, 31 can be varied asrequired to satisfy the needs of stators of different axial lengths,while the connecting portions 33, 35 must be small enough to easilyenter stator slot openings.

Insulators as generally illustrated in FIG. 6 have been made heretoforeby relatively expensive processes. For example, an entire insulator hasbeen cut from a single wide strip of polyester material in which casethe window between end portions 29 and 31, and between the connectingportions 33 and 35 would represent a large and expensive piece of scrap.Of course, smaller scrap portions from the area outside the twoconnecting portions 33, 35 would also result.

Polyester material is relatively expensive, and discarding such a largepercentage of the material as scrap leads to relatively expensive endturn insulators. In an attempt to eliminate this costly scrap, twonarrow strips of polyester material have been provided with two endportions spot-welded thereto. The new and improved end turn insulator ofFIG. 6 is now made possible by an economical and reliable processillustrated in FIG. 8, which process is somewhat analogous to theprocess presented by FIG. 5.

In FIG. 8, a plurality (such as two) of parallel elongated narrow flatstrips of polyester material 37 and 39 are continuously fed toward theright in FIG. 8 from a pair of reels of such material. Alternately,material may be fed from a single reel across means for splitting thesingle strip into the two strips 37 and 39.

A plurality of flat sheets 41 of polyester material are then disposedalong the parallel strips 37, 39 (for example, by feeding wide stripmaterial in a direction generally perpendicular to that of the narrowstrips and periodically severing such wide strip to deposit a flat sheet41 on the two narrow strips). The discrete sheets 41 and strips 37, 39pass under a pair of ultrasonic welding heads, each disposed inalignment with a path of a respective one of the strips, illustrated indotted lines as 43 and 45. These ultrasonic welding heads form acontinuous ultrasonic weld and secure or fasten the discrete pieces offlat sheet 41 to the pair of narrow strips 37, 39; thus forming aladder-like strip of relatively flat electrical insulators. Theseinsulators may subsequently be cut or blanked out to the form or contourillustrated at 47. Thereafter, pieces 47 are severed along a linesubstantially perpendicular to the direction of travel of the strips 37and 39, so that a single discrete piece such as piece 47 ultimatelyforms one end portion 29 of one insulator and the other end portion 31of another insulator. As clearly revealed in FIG. 6, ultrasonic weldingis accomplished so that no unattached extremities of the legs, strips orsegments 33, 35 exist. Thus, loose ends that may snag or catch onwindings or on a stator core are avoided. In addition, it will be notedfrom FIG. 6 that the segments 33, 35 and end portions 29, 31 are weldedtogether along substantially the entire extent of the mutuallyoverlapping or overlaying portions thereof.

FIGS. 11 and 12 show the phase insulator of FIG. 6 as it is typicallyemployed in a stator assembly 110 of a dynamoelectric machine. The useof such insulator is well known to those skilled in the art, thereforeFIGS. 11 and 12 will not be explained in great detail. A connectioninsulator 121, of my U.S. Pat. No. 3,748,510, is shown only forillustration purposes, but it will be understood that tubular insulator11 of FIG. 1 could be used in a similar manner. Therefore, asillustrated, the phase insulator will provide a layer of insulationbetween connections contained within insulator 121 and winding end turnportions 117, 118. Accordingly, with wall 138 of the insulator 121positioned against a face of phase insulator end portions 31 and 31' adouble layer of positive insulation between winding end turn portions117, 118 adjacent thereto and connections will be provided. Phaseinsulator end portion 29 is positioned between end turn portions ofdifferent winding phases at the opposite end of stator core 111 fromphase insulator portion 31. For completeness of description, it shouldbe noted that connection receiving portion 125 of insulator 121 includesa receptacle, open at 123, that receives a connection with external leadwire 124. Another external lead wire 128 is connected to winding leadwire 119. The connection 122 has been formed with a mechanical crimptype connection 120.

More specifically and as clearly taught by the schematic representationof FIG. 8, the flat sheet 41 of electrical insulating material ispositioned in overlapped relationship across strips 37, 39 at Station A.Flat sheet 41 may be a pre-cut segment of insulating material or may bea portion of a continuous length of insulating material that is fed intooverlapping relationship relative to the parallel strips 37, 39, andthen severed to make flat sheet 41. At Station B ultrasonic weldingheads 43, 45 weld the relatively overlapped or overlayed portions offlat sheet 41 and strips 37, 39 together. Welding heads 43, 45 are shownin dotted lines and it is preferable to have them located adjacent tosheet 41; therefore at Station A sheet 41 is positioned above or belowstrips 37, 39, depending on whether heads 43, 45 are above or belowstrips 37, 39. Portions of sheet 41 are removed at Station C to givesheet 41 a contoured configuration 47 better illustrated by severedpieces 47 at Station D. The ultrasonic weld has attached extremities ofstrip 37, 39 to pieces 47 as illustrated at Station D. Piece 47 could besevered simultaneously with the forming step accomplished at Station C,but it is preferred to contour or form the shape (configuration) ofpiece 47 at Station C and subsequently sever two adjacent pieces 47(e.g., at another Station D) as clearly represented in FIG. 8.

The ultrasonic welding heads 43 and 45 join each flat sheet 41 to thestrips 37 and 39 along a substantially continuous seam running generallyin the direction of elongation of the strips 37 and 39. Welding head 45(it being noted that head 43 is the same as head 45) is betterillustrated in FIGS. 9 and 10.

FIG. 10 illustrates the welding head 45 looking in the direction ofelongation of the strips 37 and 39. Welding head 45 comprises avibration transmitting portion 48, and a tip portion 49. The tip portion49 has a work piece engaging surface 51 which, as illustrated in FIG. 9,cooperates with a support member 53. The support member 53 and workpiece engaging surface 51 are biased toward one another in knownfashion, with the two superposed pieces of polyester material 39 and 41therebetween. The vibration transmitting portion 48 transmits ultrasonicvibrations to the work piece engaging surface 51. This in turn induces aweld along the interface of layers 39 and 41. At least the work pieceengaging surface 51 is surface hardened to prevent excessive wear due tothe continuous nature of the weld. However, the vibration transmissioncharacteristics of the tip are not adversely affected. Moreover,cracking of hardened tip surfaces has not been experienced.

As seen in FIGS. 7 and 9, the ultrasonic welding process causes a slightdiminution in thickness of the joined materials. The typicalpolyethylene terephthalate insulating strips employed to make theinsulator of FIG. 6 were about 0.003 inch thick, but the resultingthickness of a typical weld region was only about 0.004 inch thick.However, this 0.002 inch loss of total two layer thickness does notimpair the insulating qualities of the resulting product.

The art of sonically or ultrasonically welding has previously beendeveloped and is represented, for example, by patents that are assignedto Branson Instruments, Incorporated, of Stamford, Conn. Some of theBranson owned patents, the disclosures of which are incorporated hereinby reference, are U.S. Pat. Nos. 3,224,916; 3,367,809; and 3,499,808. Aspreviously stated, common materials (e.g., cold drawn or cold rolledsteel) may be used for welding tips after it has been case hardened. Theexact degree of hardness of the tip is not critical, so for teachingpurposes only, it is noted that the tools herein shown had a surfacehardness of about 65, Rockwell C scale; and were case hardened to adepth of about 0.021 of an inch. These tools, when energized at 20,000hertz, did not crack and did not show evidence of wear when strips 37,39, and sheet 41 (of FIG. 8) were 0.0075 of an inch thick Mylar; andwhen strip 13 (FIGS. 2 and 4) was made of different thicknesses (e.g.,0.003, 0.005, and 0.010 of an inch thick) Mylar; even though the tips 25and 49 were continually energized during formation of insulatorsembodying the invention as described above.

While the present invention has been described with respect to preferredembodiments thereof, numerous modifications will suggest themselves tothose of ordinary skill in the art. Accordingly the scope of the presentinvention is to be measured only by that of the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:
 1. A between-phase insulator for insulating different phasewindings from one another in a stator of an electric motor, the statorhaving a plurality of spaced-apart slots therein, the insulatorcomprising first and second sheets of insulating sheet material, saidfirst and second sheets being spaced apart a distance greater than thelength of the slots, at least first and second elongate spaced-apart,generally parallel pieces of insulating material connecting said firstand second sheets together, the spacing between said at least first andsecond pieces being a multiple of the spacing between the slots, each ofsaid at least first and second pieces having a width adapted forentering one of the slots and overlaying a previously formed portion ofone of the phase windings therein whereby a subsequently formed portionof another of the phase windings in the one of the slots will beinsulated from the previously formed portion, said first and secondsheets being adapted for overlapping previously formed end turn portionsof the one phase winding whereby subsequently formed end turn portionsof the another phase winding will be insulated from the previouslyformed end turn portions, opposite ends of each of said at least firstand second pieces overlapping each of said first and second sheets, andan ultrasonic weld attaching the overlapped portions of said at leastfirst and second pieces and said first and second sheets, respectively,said ultrasonic weld reducing the thickness of said overlapped portionsby an amount which does not impair the insulating qualities of thebetween-phase insulator.
 2. A between-phase insulator as set forth inclaim 1 wherein said ultrasonic weld comprises a weld seam running alongsaid at least first and second pieces so as to attach the overlappedportions of said at least first and second pieces and said first andsecond sheets, respectively.
 3. A between-phase insulator as set forthin claim 1 wherein said first and second sheets each includes a pair ofopposite edges extending generally transversely with respect to said atleast first and second pieces, said opposite ends of said at least firstand second pieces overlapping each of said first and second sheetsbetween said opposite edges thereof, respectively.
 4. A between-phaseinsulator as set forth in claim 3 wherein said ultrasonic weld comprisesa weld seam running generally along said opposite ends of said at leastfirst and second pieces between said opposite edges of said first andsecond sheets to effect the attachment of said elongate pieces and saidfirst and second sheets generally at the overlapped portions thereof. 5.A between-phase insulator as set forth in claim 3 wherein said oppositeends of said at least first and second pieces overlap said first andsecond sheets generally from one of said opposite edges to the other ofsaid opposite edges thereof, respectively, and said ultrasonic weldcomprises a generally continuous weld seam running along said oppositeends of said at least first and second pieces generally from said oneopposite edge of said first and second sheets to said other oppositeedge thereof to effect the attachment of the overlapped portions of saidat least first and second pieces and said first and second sheetsleaving no unattached extremities of said at least first and secondpieces, respectively.
 6. A ladder-like assembly adapted for producingbetween-phase insulators for insulating different phase windings fromone another in a stator of an electric motor with the stator having aplurality of spaced-apart slots therein, the assembly comprising atleast first and second generally parallel extending spaced-apart stripsof insulating material, a plurality of spaced-apart sheets of insulatingsheet material disposed generally transversely to the parallel extent ofsaid at least first and second strips and overlapping each of said atleast first and second strips generally between a pair of opposite edgesof each of said sheets, said at least first and second strips beingspaced apart a distance equal to a multiple of the spacing between theslots, adjacent ones of said sheets being spaced apart a distancegreater than the length of the slots, each of said at least first andsecond strips having a width adapted for entering one of the slots,ultrasonic weld means for connecting together the overlapping portionsof said at least first and second strips and said sheets, saidultrasonic weld means reducing the thickness of said overlappingportions by an amount which does not impair the insulating qualitiesthereof, and each of said sheets and said at least first and secondstrips being adapted to be severed in the direction generally transverseto the parallel extent of said at least first and second strips whereby,when severed, each adjacent pair of severed sheets connected together bysaid at least first and second strips forms one of the between-phaseinsulators.
 7. A ladder-like assembly as set forth in claim 6 whereinsaid ultrasonic weld means connects together the overlapping portions ofsaid adjacent sheet pair and said at least first and second strips, whensevered, forming the one between-phase insulator at least adjacent apair of opposite ends of said at least first and second strips, whensevered, respectively.